Southern Sudanese leader Salva Kiir says there is no alternative to peaceful co-existence with the north, on the eve of an independence vote.
Mr Kiir was speaking after meeting US Senator John Kerry, one of several international figures who have arrived for the vote beginning on Sunday.
The south Sudanese are expected endorse setting up the world’s newest country.
On Friday, Sudan’s President Omar al-Bashir warned the south would face instability if it voted to secede.
He told al-Jazeera TV the south did not have the ability to create a stable state or provide for its citizens.
Correspondents said Mr Bashir’s comments would infuriate the SPLM – former rebels who have ruled the south since the two-decades-long civil war ended in 2005.
The poll was part of the terms of the 2005 Comprehensive Peace Agreement (CPA), which ended the war.
As the vote neared, six people died in an attack by gunmen on Southern Sudan’s military.
Speaking in the grounds of the presidential palace in Juba, Mr Kiir said the referendum was “not the end of the journey but rather the beginning of a new one”.
“There is no substitute for peaceful coexistence,” he added.
He was speaking alongside US Senator John Kerry, who has been in dialogue with both northern and southern leaders attempting to smooth the process ahead of Sunday’s vote.
Overnight, forces loyal to rebel leader Gatluak Gai reportedly attacked forces in the Sudan People’s Liberation Army in the oil-rich area of Unity state.
Col Philip Aguer, a military spokesman, told the Associated Press that the SPLA troops had retaliated and killed four of the rebels.
UN officials confirmed that they had received reports of an attack in the area, but did not say which side had suffered the fatalities.
In an interview with the Arabic news channel al-Jazeera, Mr Bashir said he understood why many southerners wanted independence, but he expressed concern at how the new nation would cope.
“The south suffers from many problems,” he said.
“It’s been at war since 1959. The south does not have the ability to provide for its citizens or create a state or authority.”
Mr Bashir said southerners living in the north would not be allowed dual citizenship, and floated the idea of the two nations joining in an EU-style bloc.
He also raised the issue of Abyei, an oil-rich region with disputed borders.
He warned that if southerners seized the region for themselves, it could lead to war.
Analysts say Mr Bashir is under intense pressure from northern politicians, who fear that secession of the south may lead to a further splintering of the country.
North and south Sudan have suffered decades of infighting in conflicts driven by religious and ethnic divides.
Southerners have long complained of mistreatment at the hands of the Khartoum government.
At an event on Friday, former South African President Thabo Mbeki – the African Union’s mediator on Sudan – said the vote marks the “true emancipation” of the people of the south.
“The work of freedom is just at its beginning. We are confident that the southern Sudanese people have the strength and spirit to succeed in that endeavour,” he told a large crowd in Juba, the south’s capital.
Southern Sudanese will have a week to cast their vote on the future of the region, one of the least developed areas in the world.
Turnout will be important because the CPA stipulates a quorum of 60% of the 3.8 million registered voters.